rdxA基因在幽门螺杆菌对甲硝唑耐药机制中的作用

目的 探讨rdxA基因变异与幽门螺杆菌(Hp)对甲硝唑耐药之间的关系。方法 随机收集快速尿素酶试验(RUT)阳性的病人(5l例)，取胃窦部黏膜l块，在体外微需氧培养。甲硝唑耐药率检测分别用E试验和临界点药敏法。PCR扩增HA的rdxA基因片断(886bp)并测序。对耐药株和敏感株的rdxA基因序列与标准菌株HA26695相应序列进行同源性分析。结果共分离出Hp临床分离菌47株。甲硝唑用E试验法检测耐药率为34％(16／47)，临界点药敏法为31．9％(15／47)，其中15株两种方法均耐药。测序15株Hp耐药株和8株敏感株的rdxA基因片断，与标准菌株HA26695相应序列对比，15株耐药株(MtzR)的rdxA基因核酸序列相似性范围在90％-95％之间，平均为92．5％，而8株敏感株(Mtzs)相似性范围在94％—95％之间，平均为94．5％。大多数耐药株rdxA基因的变异为点变异、单个碱基插入或缺失，未发现大片段序列的插入和缺失，且突变位点是不固定的。结论 在耐甲硝唑的大多数Hp临床分离株中，rdxA基因发生多处点变异，单个碱基插入或缺失，但未发现大片段序列的插入和缺失，且变异位点是不固定的。

The role of rdxA gene in Helicobacter pylori resistant to metronidazole

Objective To investigate the relationship between the rdxA gene mutation and the resistance of H.pylori to metronidazole (Mtz).Methods All the H.pylori strains were isolated from the antrum mucosa biopsy of 51 patients who underwent gastroduodenoscopy in Fujian provincial hospital with positive rapid urea test, and were further incubated in microaerobic condition. Mtz susceptibility was determined by both E-test method and breakpoint susceptibility test (MIC>8 mg/L). The rdxA gene fragment (886 bp) of H. pylori was amplified by PCR and then sequenced. Finally polymorphism analysis was performed in the rdxA gene sequence from those strains resistant or susceptible to Mtz and standard strains H.pylori 26695. Results A total of 47 H.pylori strains were isolated from 51 patients positive for rapid urease test. Mtz resistance rate was 34% by E-test method and 31.9% by breakpoint susceptibility testing. Among them 15 strains were resistant to Mtz by the two tests. The rdxA genes of both 15 strains resistant to Mtz and 8 strains susceptible to Mtz were sequenced. Compared with that of strain H.pylori 26695, the sequence of rdxA gene nucleotide in 15 H.pyloristrains resistant to Mtz showed similarity ranging from 90% to 95% and being 92.5% on average, and the sequence of rdxA gene nucleotide in susceptible strains showed similarity ranging from 94% to 95% and being 94.5% on average. In most resistant strains, the rdxA genes occurred point mutation, single nucleotide insertion or deletion, however, the insertion or deletion of large nucleotide fragment were rare, and mutational site were variable. Conclusions The rdxA gene mutation in H.pylori strains resistant to Mtz may result from point mutations in several bases or insertional mutations or deletional mutations in one base, without insertion or deletion of large neuclectide fragment, and mutational position being variable.